Electric power drive assembly

ABSTRACT

Disclosed is a reversible, electric motor drive assembly pivotally supported from the traveling block in a derrick employed to rotate, raise, lower or otherwise handle tubular members used in the drilling and production of oil and gas wells. Hydraulic cushioning means support the assembly from the traveling block. A tubular mandrel extending through a bore in the motor shaft provides a conduit for introducing drilling fluid to a drill string connected to the rotating output drive stem of the assembly. The assembly is equipped with a pneumatically operated friction brake to permit precise and rapid alignment of equipment carried by the stem with tubular members to be handled. A locking means is employed to prevent loosening of the mandrel during reverse rotation of the stem. The reduction gearing in the assembly is immersed in oil and functions as a pumping mechanism to provide improved oil cooling and lubrication while magnetic drain plugs in the gear housing remove metal debris from the circulating oil.

United States Patent Slator et a1.

1 Aug. 26, 1975 1 ELECTRIC POWER DRIVE ASSEMBLY [75] Inventors: Damon T.Slator; Cicero C. Brown,

both of Houston, Tex.

[73] Assignee: Brown Oil Tools, Inc., Houston,

Tex.

[22] Filed: 4 Nov. 21, 1973 [211 App]. No.: 4l8,065

[52] US. Cl. 173/57; 74/411.5; 74/467; 173/164; 285/89 [51] Int. Cl.E21B 19/16 [58] Field of Search 173/57, 164; 175/170, 85;

[56] References Cited UNITED STATES PATENTS 2,032,732 3/1936 Zcrbe74/467 2,677,440 5/1954 Willis 184/625 X 3,214,198 10/1965 Pcuchmaur285/355 X 3,312,294 4/1967 Wilson 175/85 X 3,623 558 11/1971 Brown173/57 3,696,872 10/1972 Jonsson 173/164 X 5 7 ABSTRACT Disclosed is areversible, electric motor drive assembly pivotally supported from thetraveling block in a derrick employed to rotate, raise, lower orotherwise handle tubular members used in the drilling and production ofoil and gas wells. Hydraulic cushioning means support the assembly fromthe traveling block. A tubular mandrel extending through a bore in themotor shaft provides a conduit for introducing drilling fluid to a drillstring connected to the rotating output drive stem of the assembly. Theassembly is equipped with a pneumatically operated friction brake topermit precise and rapid alignment of equipment carried by the stem withtubular members to be handled. A locking means is employed to preventloosening of the mandrel during reverse rotation of the stem. Thereduction gearing in the assembly is immersed in oil and functions as apumping mechanism to provide improved oil cooling and lubrication whilemagnetic drain plugs in the gear housing remove metal debris from thecirculating oil.

PATENTED 2 1975 WN V/Z I I, w 7 ill! I l z ELECTRIC POWER DRIVE ASSEMBLYRELATED APPLICATIONS AND PATENTS This application is related to theinventions described in US. Pat. application Ser. No. 130,597 filed Apr.2, 1971 and now U.S. Pat. No. 3,766,991 entitled Electric Power Swiveland System for Use in Rotary Well Dril' ling, and in US. Pat.application Ser. No. 206,325 filed Dec. 9, 1971 and now US. Pat. No.3,774,697 entitled Rotary Drive Assembly for Handling Tubular Members,both of said inventions as well as the present invention being assignedto a common assignee.

BACKGROUND OF THE INVENTION 1. Field of the Invention The presentinvention relates to means for handling tubular fluid conductingmembers. In the specific application to be described, the presentinvention relates to vertically movable powered drive means forimparting rotary, vertical and pivotal motion to drill pipe and othertubular well members employed in the drilling and production ofpetroleum wells.

2. Brief Description of the Prior Art In the conventional method ofdrilling wells, large internal combustion engines or other power sourcesare employed to rotate a rotary table set in the floor of a drillingderrick. Rotary motion of the rotary table is conveyed to a square kellywhich is free to slide vertically through the rotary table while it isrotated by the table. The lower end of the kelly is threadedly engagedto the upper end of a string of drill pipe and the rotary motion iscarried to a bit located at the lower end of the string.

As lengths of pipe are added to or removed from the drill string, it isnecessary to employ auxiliary equipment such as wrenches, tongs, ropesand chains to threadedly engage and disengage the pipe members employedin the string. The technique, which is well known, is slow and extremelydangerous.

Other operations conventionally employed during the drilling ofa wellmay require cocking the kelly over to connect into or release a shortlength of drill pipe. The cocking and threading or unthreading requiresmanual movement of the heavy equipment away from its normal verticalposition which again necessitates the use of cumbersome, dangerousequipment.

As described in the prior related patent applications, a power swivel ofthe type referred to herein may be used to raise, lower, rotate andpivot pipe members, and any other equipment employed in drilling andcompleting a well. The ease with which such a swivel may be raised,lowered or pivoted, as well as the operators ability to manipulate thedevice automatically from a control panel, makes the task of making orbreaking strings, or handling other equipment, faster and safer. Whilethe apparatus of the related applications have substantially reducedmany of the foregoing problems, there has been a need for improvedcontrol over the angular positioning of the power drive stem in thepower swivel. Such a need arises for example when elevators are carriedby the drive stem and it is desired to align the access opening in theelevators with a length of pipe .which is to be moved. Simple reversalof the polarity of the electrical power supplied to the motor functionsto brake the stem rotation but does not operate to hold the sternstationary. Moreover, several repeated turns of the stem may be requiredbefore the stern comes to rest at the desired angular position.

During the process of working a well, and in particular when a pipestring is being broken, there are times when the swivel stem must beoperated in reverse rotation. The fluid conducting mandrel that passesthrough the center of the swivel and of the motor, and which is used toconduct drilling mud and other fluid to the well, as described in US.Pat. application Ser. No. 130,597 may tend to loosen, due to fluid drag,where conventional right-hand threads are used to secure the mandrel tothe stem.

SUMMARY OF THE INVENTION The assembly of the present invention providesvertical, rotary and angular movement in tubular well pipes as requiredin the drilling and completion of petroleum wells. These needs areprovided without the use of cumbersome rotary tables and slow, dangerousauxiliary equipment. In the present invention, a reversible electricmotor with reduction gearing is mounted as a vertically and pivotallymovable rotary drive or power swivel assembly in a well derrick, and isemployed to handle the tubular members used in the drilling andproduction of a well.

An annular brake drum is rigidly attached, concentrically, to the outputdrive stem of the assembly to assist in precisely orienting the stem.Pneumatically activated annular brake shoes, rigidly mounted ultimatelyto the assembly housing, are selectively operable to engage the brakedrum to prevent or stop rotation of the swivel stem and whateverequipment is attached thereto. With this latter improvement, theoperator need no longer rely on a hit-or-miss approach in orienting thedrive stem and the equipment attached thereto in order to make a unionwith other equipment.

Extensive hollow regions within the gear housing permit increasedcirculation of lubricating and cooling fluid around the bearingssupporting and aligning the swivel stem. In addition, a pumping actionis provided by the mating of gear teeth to further enhance thecirculation of the lubricant-coolant. One or more magnetic drain plugsin the lower portion of the swivel housing collect metal shavings thatresult from wear. Draining and replacement of the lubricating oil, aswell as removal of the collected metal shavings are effected by merelyremoving the drain plugs.

The mandrel passing through the motor and drive stem, and used tocommunicate drilling fluid to the drill string, is threadedly connectedto the inside of the stem at a point below the swivel. This connectionis secured by a lock nut which is threadedly joined to the interior ofthe stem by threads having a thread lead which is less than that in themandrel connection. The lock nut functions to tighten against the baseof the mandrel when the assembly is undergoing reverse rotation andprevents the mand rel from loosening from the stem.

These and other features and advantages of the present invention will bebetter understood from the following specification, the related drawingsand the claims.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a vertical elevation inpartial section illustrating a preferred form of the swivel and brakesystem of the present invention; and

FIG. 2 is an enlarged scale insert from FIG. 1 showing details in theconstruction of the lubricant-coolant pumping means of the presentinvention.

DESCRIPTION OF THE ILLUSTRATED EMBODIMENT The assembly of the inventionis indicated generally at in FIG. 1. The assembly includes a mainhousing 17 in the form of a substantially annular, hollow body whichencases the upper end of a rotatable output drive or swivel stem 18 andreduction gears connected between a motor shaft and the stem. A flowpath 11 extends through the housing l7 to supply lubricant to thevarious internal components. The upper end of the housing 17, which isclosed over by a circular, centrally apertured plate 12, includes tworadially extending diametrically opposed suspension ears 13 and 33 usedto suspend the assembly 10 from the derrick (not shown).

A tubular sleeve 37, having an axial throughbore 38, is screwed into thelower end of a vertical bore 34 formed through the suspension ear 33,which is similar in construction to the ear 13. A bore 36 through theear 35 of plate 12 registers with the bore 34. The bore 38 defines apressure cylinder 38a adapted to receive a piston 39 formed with a lowerhead 40 fitted with seal rings 41 and 42 for slidable sealing engagementwith the wall of bore 38. Piston 39 extends upwardly through bores 34and 36 which are provided with packings 43 and 44 respectively, sealingwith the piston to close the upper end of the cylinder. A nut 43a screwsinto the bore 34 in the suspension ear 33, keeping the seal 43 underpressure, and providing a smooth base, flush with the top of the ear 33,upon which the seal 44 may be seated. The upper end portion of piston 39which projects above plate 12 is provided with an externally threadedpin 45 which is screwed into a hanger cap 46. The latter has an upwardlyextending lug 47 which is received in a clevis 48 and pivotally securedthereto by means of a transversely extending pivot pin 49. The cleviseson both sides are secured to the opposite ends of a bail 50 by means ofwhich the entire device is swung (in a manner not illustrated) from ahook or like connection of a travelling block employed in conventionalrotary drilling and suspended from drilling cables in a conventionaldrilling derrick.

Each of the cylinders 38a is in communication with a port 51 which isconnected to a conduit 52 leading to a closed reservoir of an inertpneumatic fluid (not shown) such as nitrogen gas, which is keptcontinuously pressurized.

The outer ends of ears 33 are fitted with trunions 72 journalled in theends of guide arms 73 which connect to guide sleeves (not shown)disposed for sliding movement on vertically positioned guide bars (notshown) suitably mounted in the drilling derrick in which the powerswivel is suspended. The trunions thus provide a pivoting connectionbetween the power swivel and the guide sleeves so as to permit the powerswivel to be tilted at an angle to the vertical when required.

In order to effect tilting of the power swivel when desired, a fluidpressure actuated tilting jack (not shown) is connected between thetravelling block supporting the power swivel and housing 17 of the powerswivel. Such a tilting jack is disclosed in US. Pat. application Ser.No. 130,579, and further information regarding the mounting and use ofthe assembly 10 may be derived from the said patent application as wellas US Pat. application Ser. No. 206,325.

A reversible electric motor encased within a motor housing M is employedto provide power in the form of rotary motion in a hollow drive shaft 16having an axial bore 16a. Bolts 15 secure the motor housing M to the topplate 12. The lower end of the drive shaft 16 is locked to a centralspur or pinion gear 27 equipped with gear teeth 27a (FIG. 2). An annularbearing mount 53 encircles the gear 27 and supports an inner race member54 on inclined roller bearings 55. An outer race 56 for the bearings 55is mounted concentrically within the circular plate 12. The rollerbearings 55 are employed for preloading the rotatable drive assembly andprovide both axial and radial friction reducing support.

Three planetary gears, one shown generally at 57, are mounted for rotarymotion about shafts secured to a circular mounting head formed at theupper end of the stem 18. The lower end of the stem 18, which extendsdownwardly through bore 14 in the housing 17 and below the brake system90, is internally threaded to receive other equipment. The centers ofthe gears 57 are positioned on the same radius and are circumferentiallyspaced 120 from each other. The three gears 57, which are the same, willbe described with specific reference only to the one gear shown. Thisgear 57 includes a central shaft 29 which is mounted in a receivingrecess 18a formed in the top surface of the mounting head on the stem18. Socket head bolts 30 hold the shaft 29 in firm engagement with thestem 18 and ball bearings 58 mount an annular gear ring 26 about theshaft 29. The ring 26 is equipped with external gear teeth 28 which meshwith the gear teeth 27a on the pinion gear 27 and also mesh with gearteeth 31a formed internally of a large ring gear 31. The ring gear 31 isrigidly secured to the plate 12 by suitable socket head bolts 32.

Rotary and axial support for the large weight which is to be suspendedfrom the stem 18 is provided by tapered roller bearings 59 supportedbetween lower and upper races 19 and 19a, respectively. The lower race19a is supported on an annular H-beam collar 20 which in turn issupported on an internal shoulder 21 formed in the housing 17. Aconventional strain gauge is attached to the upstanding web 20aconnecting the upper and lower portions of the collar 20 and suitableelectrical leads 70a extend to an external control panel (not shown) toprovide an input signal to a transducer which forms a visible indicationof the weight being supported by the stem 18.

At the lower end of the housing 17, the stem 18 is supported radially byroller bearings 22. An annular fitting 23 secured to the base of thehousing 17 by bolts 25 mounts a resilient seal 24.

Magnetic drain plugs (one shown) are threadedly inserted in verticalholes 81 (one shown) located in an annular arrangement about the lowestportion of the passage 11 in the housing 17. Passageways 11a (oneshown), forming a portion ofthe flow passage 11 in the housing 17, areradially aligned with corresponding holes 23a in the annular fitting 23,just below each roller bearing 22. An enlarged spacing 71 (FIG. 2) inthe passage 11 forms a passageway above gear teeth 27a and 28, betweenthe bearing mount 53 and the pinion gear 27, and up to the bearings 55.

The mating of the pinion gear with the planar gear displaces the oillocated between the teeth of each gear, causing this oil to flowparallel to the cylindrical axes of the gears. The open space 71 abovethe region of the meshing of the gear teeth is greater than that belowthe gears, permitting a greater amount of the moving oil to flow intothe upper space 71 as compared with that flowing in the oppositedirection. In this way, as the gears turn in either direction, oil iscirculated upwardly to flow over and around the bearings 55, while moreoil is drawn into the region of the meshing teeth from below, and acontinuous pumping action is established to keep the oil circulating.

A tubular mandrel 60 extends upwardly through the bore of the stem 18,being threadedly connected to the stem at a point at the bottom of abrake system 90 by a threaded connection 61. The mandrel extendsupwardly through the bore of pinion gear 27 and the bore 16a of themotor shaft 16 and thence through a swivel housing 62. The mandrel 60continues externally to appropriate fittings (not shown) required forthe conduc' tion of drilling mud or other fluid to the drill stringthrough the bore of the mandrel 60.

Viscous drag between the interior surface of the mandrel 60 and thefluid it contains tends to unthread the mandrel during reverse rotationof the stem 18. A lock nut 63 is threadedly connected to the interior ofthe stem 18 just beyond the mandrel-to-stem connection 61. The threadlead of the lock nut connection is made smaller than that of the mandrelconnection. The lock nut 63, having a smaller surface area exposed tothe fluid within than does the mandrel 60, will experience smallerviscous drag than will the mandrel. Furthermore, with a smaller threadlead, the lock nuts axial movement will be less than that of the mandrelfor one turn. Since the mandrel, upon loosening, must move in thedirection of the lock nut, any loosening of the mandrel induced byreverse rotation of the swivel stem will be blocked by the slower movinglock nut. This locking force increases as the forces tending to rotatethe lock nut and mandrel increase.

The brake system 90 is enclosed by a hollow, annular housing 91, theupper portion of which is composed of a flange 91a welded to a ring 91bwhich is welded to a second, smaller flange 910. The housing 91 is thussuspended by flange 9lc which is connected, through an annular fitting82, to the annular fitting 23 by bolts 25. The lower portion of thehousing 91 is formed by a flanged ring 91d which is welded to the flange91a.

An annular sleeve 92 is locked to and thereby rotates with swivel stem18. An annular brake drum 93 is bolted to the sleeve 92 by bolts 94. Theouter annular surface 93a of the brake drum 93 provides the brakingmeans when contacted by brake shoes 95 (only one shown).

A pneumatic connector 96, suspended from the housing 91 by a bolt 96a,leads from a pneumatic supply line (not shown) to a flexible member 96b,which is designed to inflate with pressurized air supplied from thepneumatic line. Inflation of the member causes the member to pressagainst an enclosing flexible member 96c. This in turn causes the brakeshoes 95 carried on the member 960 to be forced inwardly against thebrake drum 93a. The brake shoes comprise a plurality of plates of anysuitable material suspended annularly about the inner surface of theflexible member 96c. The

flexible member 96c is resilient and causes retraction of the brakeshoes 95 and collapse of the flexible member 96b when the pressurewithin the flexible member 96b is relieved through the pneumatic supplyline.

The sleeve 92 is equipped with a vertical, cylindrical bore 92a pluggedat the'top end to form a flow passage rotating with the swivel stem 18.The bottom of the passage 92a is threaded to receive a hose fitting (notshown). A circumferential recess 92b in the sleeve 92 communicatesbetween the passage 92a and a passageway 82a in the vertical wall of theannular fitting 82. The passageway 82a is aligned with an opening in thering 91b of the housing 91 to permit access, via a conduit (not shown),to the passageway 82a, which is threaded to receive a hose fitting (notshown). Double resilient seals 83 above and below the region of thepassageway 82a preserve the integrity of the communication from thepassage 92a to the passageway 82a to the conduit.

OPERATION OF THE ASSEMBLY ln operations such as making or breaking apipe string, attaching orienting equipment for directional drilling,etc., the operator is periodically required to stop and hold the swivelstem 18 steady in some particular angular orientation. When this needarises, the operator actuates the brake system by increasing thepneumatic pressure via the conduit (not shown) connected to thepneumatic connector 96. The flexible member 96b is thereby inflated,pressing against the flexible member 960, causing the brake shoe to beforced against the brake drum 93. Friction between the brake shoe 95 andthe outer surface 93a of the brake drum 93 supplies the braking action,which prevents the brake drum 93 from rotating with respect to the brakeshoe 95. Since the brake shoe is held fixed to the brake system housing91, which is rigidly connected to the swivel housing 17, and since thebrake drum 93 is rigidly connected to the stem 18, activation of thebrake system in this manner prevents rotation of the stem 18 withrespect to the housing 17. The operator may thus align the stem,including whatever equipment may be attached thereto, and selectivelylock'the stem against rotation about its axis.

Once the activity necessitating the locking of the stem in position iscompleted, the operator need only reduce the pneumatic pressure via theconduit to the connector 96. The resilient member 960 will collapse,causing the retraction of the brake shoe 95 from the brake drum surface93a. The stem is then released, and the operator may continue withrotational motion, if desired.

Once the mandrel 60 is installed and screwed into place within the stem18, the lock nut 63 is fastened below the mandrel, tightly against thebottom face of the mandrel. Any viscous drag or other retarding forceexerted on the mandrel during forward rotation of the stem 18 onlyserves to tighten both the mandrel 60 and the lock nut 63 in theirrespective threaded connections to the stem 18. In reverse rotation,however, the retarding forces tend to unthread the mandrel 60 and thelock nut 63. The mandrel attempts to overrun the slower moving lock nut,which in turn jams the two members together to prevent further movement.Thus, if the mandrel tends to loosen, it will be blocked by the locknut, with the result that the mandrel is effectively locked in place inits attachment to the swivel stem 18.

The housing 17 is filled with an appropriate lubricating and coolingfluid such as a light weight motor oil. As the assembly is drivenrotationally by the motor M, the meshing of the pinion gear 27 with theplanatary gears 57, combined with the increased volume above the regionof the mating of the teeth of these gears, pro duces a circulatingpumping action. Oil is thus forced over the roller bearings 55, and thenthrough the rest of the expanded cavity 11 within the housing 17.

The passageway formed at 11a and 23a through the housing 17 and theannular fitting 23 respectively allows circulation of the oil to theroller bearings 22. The roller bearings 59 giving vertical support toswivel stem 18 are also open to the oil circulation due to the shape ofthe passageway 11 within the housing 17. The described oil circulationserves to keep all exposed parts within the housing 17 lubricated, tocool parts that tend to heat up during operation of the swivel, and toflush all metal fillings and chips and other metallic debris producedduring operation. In the process of circulating around the flow path 11,the oil moves this debris past the magnetic drain plugs 80. These plugsmagnetically attract and hold the metallic debris, removing it from thecirculating oil. The debris can then be periodically removed by removingand cleaning the magnetic drain plugs 80.

The flow passage 92a in the sleeve 92 which rotates with the swivel stem18 permits a pneumatic, hydraulic, or other type connection between anyequipment attached to and rotating with the swivel stem 18 and anexternal source (not shown). A hose connection is made from saidrotating equipment via the threaded bottom of the passage 92a.Communication of the fluid to or from the external source is then madevia the groove 92b, the passageway 82a, threaded for an external hosefitting, and thence to the source via said hose (not shown).

The foregoing disclosure and description of the invention isillustrative and explanatory thereof, and various changes in the size,shape and materials as well as in the details of the illustratedconstruction may be made within the scope of the appended claims withoutdeparting from the spirit of the invention.

We claim:

1. A rotary drive assembly for rotating tubular members comprising:

a. motor means for developing rotary power in said assembly;

b. an axially extending rotatable stem means rotatably powered by saidmotor means; and

c. friction braking means included in said assembly for selectivelystopping and/or retaining said stem means at a fixed angular positionabout its axis.

2. A rotary drive assembly for rotating tubular members as defined inclaim 1 further including fluid powering means for selective activationof said friction braking means.

3. A rotary drive assembly for rotating tubular members as defined inclaim 1 further including:

a. a tubular mandrel means extending axially through said stem means;and

b. locking means, movable relative to said mandrel means, for retainingsaid mandrel means within said stem means, said locking means includingmeans for providing increasing locking forces in response to increasingrotational forces tending to displace said mandrel means within saidstem means.

4. A rotary drive assembly for rotating tubular members as defined inclaim 3 further including fluid powering means for selective activationof said friction braking means.

5. A rotary drive assembly for rotating tubular members comprising:

a. motor means for developing rotary power in said assembly;

b. an axially extending rotatable stem means rotatably powered by saidmotor means;

c. gear reduction means disposed between said motor means and said stemmeans;

(1. housing means enclosing said gear reduction means;

e. fluid means contained within said housing means;

f. pumping means for preferential circulation of said fluid meansthrough flow passage means provided within said housing means, saidpumping means including differential volume regions provided adjacentthe axial ends of meshing gear means in said reduction means to induce acirculatory flow of fluid; and

g. magnetic means for removing metallic debris from said circulatingfluid means.

6. A rotary drive assembly for rotating tubular members as defined inclaim 5 further including friction braking means for selectivelystopping and/or retaining said stem means at a fixed angular positionabout its axis.

7. A rotary drive assembly for rotating tubular members as defined inclaim 6 further including fluid powering means for selective activationof said friction braking means.

8. A rotary drive assembly for rotating tubular members as defined inclaim 5 further including:

a. tubular mandrel means extending axially through said stem means; and

b. locking means, movable relative to said mandrel means, for retainingsaid mandrel means within said stem means, said locking means includingmeans for providing increasing locking forces in response to increasingrotational forces tending to displace said mandrel means within saidstem means.

9. A rotary drive assembly for rotating tubular members as defined inclaim 8 further including friction braking means for selectivelystopping and/or retaining said stern means at a fixed angular positionabout its axis.

10. A rotary drive assembly for rotating tubular members as defined inclaim 9 further including fluid powering means for selective activationof said friction braking means.

1. A rotary drive assembly for rotating tubular members comprising: a.motor means for developing rotary power in said assembly; b. an axiallyextending rotatable stem means rotatably powered by said motor means;and c. friction braking means included in said assembly for selectivelystopping and/or retaining said stem means at a fixed angular positionabout its axis.
 2. A rotary drive assembly for rotating tubular membersas defined in claim 1 further including fluid powering means forselective activation of said friction braking means.
 3. A rotary driveassembly for rotating tubular members as defined in claim 1 furtherincluding: a. a tubular mandrel means extending axially through saidstem means; and b. locking means, movable relative to said mandrelmeans, for retaining said mandrel means within said stem means, saidlocking means including means for providing increasing locking forces inresponse to increasing rotational forces tending to displace saidmandrel means within said stem means.
 4. A rotary drive assembly forrotating tubular members as defined in claim 3 further including fluidpowering means for selective activation of said friction braking means.5. A rotary drive assembly for rotating tubular members comprising: a.motor means for developing rotary power in said assembly; b. an axiallyextending rotatable stem means rotatably powered by said motor means; c.gear reduction means disposed between said motor means and said stemmeans; d. housing means enclosing said gear reduction means; e. fluidmeans contained within said housing means; f. pumping means forpreferential circulation of said fluid means through flow passage meansprovided within said housing means, said pumping means includingdifferential volume regions provided adjacent the axial ends of meshinggear means in said reduction means to induce a circulatory flow offluid; and g. magnetic means for removing metallic debris from saidcirculating fluid means.
 6. A rotary drive assembly for rotating tubularmembers as defined in claim 5 further including friction braking meansfor selectively stopping and/or retaining said stem means at a fixedangular position about its axis.
 7. A rotary drive assembly for rotatingtubular members as defined in claim 6 further including fluid poweringmeans for selective activation of said friction braking means.
 8. Arotary drive assembly for rotating tubular members as defined in claim 5further including: a. tubular mandrel means extending axially throughsaid stem means; and b. locking means, movable relative to said mandrelmeans, for retaining said mandrel means within said stem means, saidlocking means including means for providing increasing locking forces inresponse to increasing rotational forces tending to displace saidmandrel means within said stem means.
 9. A rotary drive assembly forrotating tubular members as defined in claim 8 further includingfriction braking means for selectively stopping and/or retaining saidstem means at a fixed angular position about its axis.
 10. A rotarydrive assembly for rotating tubular members as defined in claim 9further including fluid powering means for selective activation of saidfriction braking means.